netfilter: add helper for adding nat extension

Reduce copy-past a bit by adding a common helper.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_nat.h

@@ -48,6 +48,8 @@ unsigned int nf_nat_setup_info(struct nf_conn *ct,
 extern unsigned int nf_nat_alloc_null_binding(struct nf_conn *ct,
 					      unsigned int hooknum);
 
+struct nf_conn_nat *nf_ct_nat_ext_add(struct nf_conn *ct);
+
 /* Is this tuple already taken? (not by us)*/
 int nf_nat_used_tuple(const struct nf_conntrack_tuple *tuple,
 		      const struct nf_conn *ignored_conntrack);

net/ipv4/netfilter/iptable_nat.c

@@ -91,17 +91,9 @@ nf_nat_ipv4_fn(const struct nf_hook_ops *ops,
 	if (nf_ct_is_untracked(ct))
 		return NF_ACCEPT;
 
-	nat = nfct_nat(ct);
-	if (!nat) {
-		/* NAT module was loaded late. */
-		if (nf_ct_is_confirmed(ct))
-			return NF_ACCEPT;
-		nat = nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC);
-		if (nat == NULL) {
-			pr_debug("failed to add NAT extension\n");
-			return NF_ACCEPT;
-		}
-	}
+	nat = nf_ct_nat_ext_add(ct);
+	if (nat == NULL)
+		return NF_ACCEPT;
 
 	switch (ctinfo) {
 	case IP_CT_RELATED:

net/ipv4/netfilter/nft_chain_nat_ipv4.c

@@ -48,15 +48,9 @@ static unsigned int nf_nat_fn(const struct nf_hook_ops *ops,
 
 	NF_CT_ASSERT(!(ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)));
 
-	nat = nfct_nat(ct);
-	if (nat == NULL) {
-		/* Conntrack module was loaded late, can't add extension. */
-		if (nf_ct_is_confirmed(ct))
-			return NF_ACCEPT;
-		nat = nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC);
-		if (nat == NULL)
-			return NF_ACCEPT;
-	}
+	nat = nf_ct_nat_ext_add(ct);
+	if (nat == NULL)
+		return NF_ACCEPT;
 
 	switch (ctinfo) {
 	case IP_CT_RELATED:

net/ipv6/netfilter/ip6table_nat.c

@@ -90,17 +90,9 @@ nf_nat_ipv6_fn(const struct nf_hook_ops *ops,
 	if (nf_ct_is_untracked(ct))
 		return NF_ACCEPT;
 
-	nat = nfct_nat(ct);
-	if (!nat) {
-		/* NAT module was loaded late. */
-		if (nf_ct_is_confirmed(ct))
-			return NF_ACCEPT;
-		nat = nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC);
-		if (nat == NULL) {
-			pr_debug("failed to add NAT extension\n");
-			return NF_ACCEPT;
-		}
-	}
+	nat = nf_ct_nat_ext_add(ct);
+	if (nat == NULL)
+		return NF_ACCEPT;
 
 	switch (ctinfo) {
 	case IP_CT_RELATED:

net/ipv6/netfilter/nft_chain_nat_ipv6.c

@@ -47,15 +47,9 @@ static unsigned int nf_nat_ipv6_fn(const struct nf_hook_ops *ops,
 	if (ct == NULL || nf_ct_is_untracked(ct))
 		return NF_ACCEPT;
 
-	nat = nfct_nat(ct);
-	if (nat == NULL) {
-		/* Conntrack module was loaded late, can't add extension. */
-		if (nf_ct_is_confirmed(ct))
-			return NF_ACCEPT;
-		nat = nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC);
-		if (nat == NULL)
-			return NF_ACCEPT;
-	}
+	nat = nf_ct_nat_ext_add(ct);
+	if (nat == NULL)
+		return NF_ACCEPT;
 
 	switch (ctinfo) {
 	case IP_CT_RELATED:

net/netfilter/nf_nat_core.c

@@ -358,6 +358,19 @@ get_unique_tuple(struct nf_conntrack_tuple *tuple,
 	rcu_read_unlock();
 }
 
+struct nf_conn_nat *nf_ct_nat_ext_add(struct nf_conn *ct)
+{
+	struct nf_conn_nat *nat = nfct_nat(ct);
+	if (nat)
+		return nat;
+
+	if (!nf_ct_is_confirmed(ct))
+		nat = nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC);
+
+	return nat;
+}
+EXPORT_SYMBOL_GPL(nf_ct_nat_ext_add);
+
 unsigned int
 nf_nat_setup_info(struct nf_conn *ct,
 		  const struct nf_nat_range *range,
@@ -368,14 +381,9 @@ nf_nat_setup_info(struct nf_conn *ct,
 	struct nf_conn_nat *nat;
 
 	/* nat helper or nfctnetlink also setup binding */
-	nat = nfct_nat(ct);
-	if (!nat) {
-		nat = nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC);
-		if (nat == NULL) {
-			pr_debug("failed to add NAT extension\n");
-			return NF_ACCEPT;
-		}
-	}
+	nat = nf_ct_nat_ext_add(ct);
+	if (nat == NULL)
+		return NF_ACCEPT;
 
 	NF_CT_ASSERT(maniptype == NF_NAT_MANIP_SRC ||
 		     maniptype == NF_NAT_MANIP_DST);